The layout of the underground group caverns of Wudongde hydropower station at the right bank has a complicated form，and the structure-controlled failure phenomena occurred frequently due to the low stress condition and unfavorable formations of rock stratum，such as high dip angle and low strike angle. In this study，the modes and causes of failure of the surrounding rock near the downstream abutment of the main powerhouse at the right bank are systematically summarized with the geological data，field surveys，traditional monitoring，micro-seismic(MS) monitoring and numerical simulation. Firstly，the essential characteristics of the failure of surrounding rocks including the failure modes，spatial locations，scale of destruction and damage process，are summarized. Secondly，the temporal variation of the micro-seismic activity and the micro-seismic precursory characteristics of the failure of layered rock during the development of the studied failure are obtained. Finally，the flexural toppling failure of the surrounding rocks and the causes of this phenomena are revealed. The influence of rock structure on the failure of the surrounding rocks near the abutment is also discussed in detail by using a comprehensive method，which incorporates the micro-seismic monitoring and numerical simulation.

The dynamic strain rate has a great effect on the dynamic deformation process of rocks. Considering the nonlinear effect of dynamic strain rate of rocks on their strength，a nonlinear dynamic strength criterion reflecting the influence of strain rate was developed based on the improvement to the existing dynamic strength criterions of rocks. With the nonlinear dynamic strength criterion proposed and the measurement method of the microelement strength considering the effect of the strain rate of rocks，a dynamic statistical damage constitutive model for rocks was proposed based on the statistical damage theory. A method for determining the model parameters based on the dynamic stress-strain curves from the dynamic triaxial test of rocks was also put forward. A method simulating the dynamic deformation process of rocks was established，which reflect the influence of not only stress state but also strain rate on the dynamic deformation process of rocks. Finally，a comparison between the experimental and theoretical curves of this model and other existing similar models was carried out and the rationality and advantage of the proposed model in this paper were demonstrated.

In this paper，a method of multi-parameter comprehensive evaluation to increase the accuracy of rock burst monitoring and pre-warning was established based on the relationships among the micro seismic parameters，stress，acoustic emission，etc. The degree of coal-rock mass deformation and fracture under loading and the parameters during the failure process were normalized. Based on the uniform risk evaluation criterion of rock burst，the rock burst risk was classified into four grades: none，weak，moderate and strong. The rock burst energy and stress conditions under the combined dynamic and static loading were theoretically analyzed，and a theory of rock burst due to the combined dynamic and static load was put forward. With the seismic computed tomography and mining-induced seismic data，the passive velocity tomography was proposed to describe the static stress field and to assess the rock burst risk quantitatively and regularly. The indexes of velocity anomaly and velocity gradient anomaly were constructed. Meanwhile，the bursting strain energy index was used for the short-term spatial-temporal monitoring of dynamic wave field and for the pre-warning of rock burst based on the seismic monitoring. The status of dynamic stress field and levels of rock burst risk can be quantitatively and rapidly analyzed in short time. The rock burst pre-warning technology of “stress field and wave field” was thus constructed. The pre-warning technology was applied in the mining areas of Yima and Datun and the comprehensive prediction accuracy reached more than 80%.

A geometric model of joint surfaces was constructed through the fractional Brown function. The finite element analysis on the basis of N-S equations was conducted to the fracture grouting process. The influence of roughness and connectivity of joint surfaces on the fracture grouting was investigated and the rationality of the modified cubic law was analyzed. When the potential of the interface layer is relatively low，the calculation results of the modified cubic law are lower than the actual values. When the contacting area is uniformly distributed，the degree of anisotropy is low and the calculated deviation is small，and vice versa. A grout spreading formula based on the modified cubic law，constitutive equation of interface layer and grout flow equation was proposed considering the grout-rock coupling effect. The calculated distance of grout spreading is greater than that without the coupling effect. The calculation deviation is also larger with the increase of grout viscosity.

During the underground excavation，the stresses in surrounding rock follow the complex paths. It is a key issue to describe the stress path and its effect on the surrounding rock correctly in underground engineering. The complex stress paths and failure modes of surrounding rock during Mine-by test tunnel excavation are discussed based on three parameters including the crack initial criterion(CIC)，the stress ratio   and the lode parameter. It is shown that the disturbance of stress field is mainly concentrated near the excavation face within the scope of the tunnel diameter and the damage of surrounding rock is controlled by the highly concentrated deviatoric stress and stress axis rotation. As the excavation face advances，the deviatoric stress concentration increases and the stress ratio reduces at the top and the bottom of the surrounding rock，where a v-shaped spalling has been formed gradually. The surrounding rock of the tunnel wall unloads gradually，and the damage is changed to be controlled by the tensile stress. The stress path of in-situ rock is more complex than that in laboratory because of the effect of stress rotation. During the excavation of Mine-by test tunnel，the rotation of the major principal stress direction is hardly changed at the top and the bottom of surrounding rock，and the intermediate principal stress and minor principal stress rotate 35.2 degrees before returning to the initial direction. Since the intermediate principal stress has exceeded the rock mass crack initiation strength(CIC＞1)，the stress rotation aggravates the damage degree of surrounding rock.

The seismic behaviors of the slope reinforced with the multi-frame beam，anchor cables and double-row anti-slide piles were investigated with the large-scale shaking table model test. The earth pressure acting on the pile，the axis force in the anchor cable，the acceleration in the slope and the deformation of the frame-beam were measured under the action of El Centro and Wenchuan-Qingping earthquake waves. The anchors and anti-slide piles perform as a collaborative structure under earthquake. The earth pressure increases with the amplitude of input seismic waves. However，The variation of anchor cable prestress is related to the stability of the slope，its value decreases firstly and then increases. The acting point of the resultant force of the active earth pressure moves up to the position of l/2. The pivots of pile embedded bedrock are varied significantly. When the peak ground acceleration of input seismic wave is less than 0.5 g，the displacement response of the frame-beam is small and the acceleration amplification effect does not exist obviously below the pile in the middle part of slope. The damage characteristics of internal slope analyzed using the Hilbert marginal spectrum theory are in agreement with the measured data.

In order to study the dynamic properties and failure characteristics of salt rock，the split Hopkinson         pressure bar(SHPB) apparatus was used to conduct impact tests of salt rock under the confining pressures of 5，15 and 25 MPa. The dynamic properties and failure characteristics were studied based on the energy dissipation principle. The energy transmitting and transformation in the whole experimental process were analyzed in details，and the effect of the confining pressure and incident energy to the energy absorption and fracture of salt rock were studied specifically. Under the same confining pressure，the hardening effect of salt rock is more obvious with the increase of the incident energy，which can be explained as the reduction of the energy transmission/absorption rate and the increase of reflection rate. At the same or similar incident energy，the flow plasticity of salt rock becomes more obvious with the increase of confining pressure，but the salt rock changes from the flow plasticity to brittle under the dynamic loads and present brittle failure in the end. The peak stresses of salt rock show the different trends with the growth of energy absorption under the different confining pressures. Under the low confining pressures，the greater the energy absorption，the higher the peak stress. The peak stress decreases dramatically with the increasing of energy absorption under the high confining pressures. The impact fracture morphology of salt rock is similar to that of other brittle rocks under the condition of confining pressures，but there are intrinsic differences in damage mechanisms.

The underground powerhouse caverns at Baihetan under construction are quite huge and have the characteristics of high side wall，large span，high geostress and complicated geological conditions. In the process of excavation unloading under high geostress，the caverns have been affected by several large staggered zones with poor ductility and mechanical properties. As a result，the rock masses with staggered zones have encountered various kinds of deformation and failure problems. On the basis of the collected data from the geological，construction，monitoring，testing and numerical analysis，the engineering properties of staggered zones are described in detail in terms of occurrence，causes and characteristics. The instances of distortion failure or destruction of engineering rock mass structure induced by the staggered zones are summarized. From the point of view of the structure controlling，the failure modes of rock masses with staggered zones are categorized into the plastic squeezing-out tensile failure，the structural stress-induced collapse/block-fall and the contact shear slip failure. The characteristics of three failure modes are studied and analyzed regarding the spatial and temporal development，the morphology，the scale of destruction and so on. The corresponding mechanisms of three kinds of failures are revealed initially. A typical example of structural stress induced collapse is presented to further explain the analysis and prediction of failure mode and supporting measures.

Current D-InSAR technology cannot fully survey the surface movement and deformation caused by the coal mining. To overcome the weakness，a method of extracting the movement and deformation from a single D-InSAR pair based on the integrated means of theoretical derivation and simulation experiments was proposed. A calculation model of the tilt，horizontal movement，curvature and horizontal deformation in any direction for all pixels by combining the subsidence of the horizontal and gently inclined coal seams and D-InSAR technology was established. The errors of tilt calculation in North-south and east-west directions are ±0.03 mm/m and ±0.02 mm/m respectively. The errors of horizontal movement calculation in north-south and east-west directions are ±1.6 mm and ±1.3 mm respectively. The errors of horizontal deformation calculation in north-south and east-west direction are ±0.04 mm/m and ±0.03 mm/m respectively. The errors of curvature deformation calculation in north-south and east-west directions are ±0.001 mm/m2 and ±0.001 mm/m2 respectively. During the period of 05-01-2012 to16-01-2012，the surface movement and deformation in north-south and east-west directions caused by the mining at workface 9310 in Nantun coal mine were calculated by using the retrieving model of movement and deformation.

The controlled microwave field(CMF) is proposed in this paper to address the technical challenge posed by the difficulty in desorption of adsorbed gas during the extraction of coal bed methane. The study on the desorption of methane in coal mass with and without the CMF action was conducted with the gas desorption system with CMF developed in-house. The mechanism of influence of the CMF on the desorption characteristics of methane in coal mass is investigated. It was proved by the experiments that the CMF enhanced the desorption of methane in coal mass and enabled a significant increase in the desorption rate of methane in the coal with the attenuation slowdown. The accumulated amount of methane desorption was increased by 1.65 up to 3.79 times. The shapes of the kinetic curve for the desorption of methane in coal mass remain consistent with or without the CMF action，which may be better depicted by the dynamic diffusion coefficient model. During the same desorbing time，the diffusion coefficient of methane in the coal mass with the CMF action is greater than that of methane without. The CMF may enhance the molecular activity and increase the diffusion coefficient of methane in the coal mass. It alters the differential diffusion resistance of the coal mass during the desorption of methane，thus enables the increase in the desorption and diffusion rate of methane in the coal mass with the decreased diffusion resistance，which promote the desorption of methane in the coal mass.

Lattice beam anchorage has been applied more and more widely in the landslide prevention，but its mechanism research is lagging far behind the practical application. The large scale physical model tests were carried out to investigate the stress state，failure mode and bearing mechanisms of the lattice beam anchorage. The results show that the fully grouted lattice beam anchorage enhances the stability of the slope. The maximum anchoring force takes place near the sliding surface and descends from the sliding surface to the two ends. The loads to the lattice beam are very small and the foundation pressure distributes as a triangle，with the maximum near the middle and tapering towards both ends. The shear deformation of the anchor arises at the slip surface and the lattice beam bends little. The whole slope slipped. The anchor is the main anti-slide member which plays an anti-shear role and the lattice beam guarantee the overall stability of the slope. The design of the fully grouted lattice beam anchorage should focused on the shear strength of the anchor，and the lattice beam should be the reinforced concrete.

he method of drainage cutoff by air filling is a new approach to improve the stability of slopes. Injecting the compressed air into the saturated soil slope forms an unsaturated zone which can prevent the water entering into the critical failure surface of the slope. In this study，laboratory experiment and numerical simulation were carried out to investigate the relationship between the air pressure and interception effect. Results show that the air filling has remarkable effect on water flow interception. For a given slope，there exist a start-up pressure and an optimal pressure of air filling. When the air pressure is greater than the start-up value，the water table can be lowered. When the pressure ranges between the start-up and optimal values，the water table decreases with the increase of air pressure. However，when the air pressure is higher than the optimal value，the water table increases with the increase of air pressure.

In this paper，the topography，landscape and geological conditions, and deformation process and failure characteristics of the super-high cut slope K227 along the expressway from Yongchun to Yongding in City Longyan of China were described. Simulation and quantitative evaluation of the deformation development of the slope were conducted with the back analysis for slope stability，the strength reduction method and the finite element modelling of excavation. A method based on the differential data of stress tensor is proposed to determine the relaxation zone due to excavation and to explain better the mechanism of unloading relaxation due to the excavation of the high cut slope. The numerical simulation faithfully reproduced the process and trending of the stress adjustment，plastic yielding，development of slip surface and deformation at all stages of the slope failure. The slope stability mildly increased in the unloading rebound stage，linearly reduced in the shearing failure stage and abruptly reduced in the instability stage. The numerical results demonstrated that the disturbance due to the fast excavation led to the potential weak layer to be fully exposed and cut off the mechanical support at the toe of the slope. The unloading relaxation and the weakened strength of the rock and soils resulted in the tension crack at the top，the shearing creep of deep weak layer and the shearing along the joints at the toe of the slope. The intermittent rainfall which increased the weight of the rock and soils and the extra pore water pressure caused the slope to slide intermittently. The slope is close to the limit equilibrium state globally and the stability may be abruptly reduced if further excavation or strong rainfall happen. Finally，the discussions and reflections on the emergency and rescue strategy，the planning of slope disaster mitigation methods and route adjustment are also presented.

The experimental research on the strength parameters of Drucker-Prager criterion, i.e. the coefficient of pressure sensitivity   and the shearing strength of cohesion  ，was rarely reported. The parameters including the internal friction angle  ，the cohesion  ，the coefficient of pressure sensitivity   and the shearing strength of cohesion   were measured simultaneously with the same group of triaxial compression tests on dense sandstone. The results show that   and   gradually increase with the plastic deformation in a decreasing rate，while   and   firstly increase to their peak values and then decrease with the plastic deformation. Five pairs of mostly used parameter conversion formulae for Mohr-Coulomb criterion and Drucker-Prager criterion were compared so that a pair of best fit conversion formulae were found with the same group of triaxial compression tests. The variation of strength parameters in Mohr-Coulomb criterion and Drucker-Prager criterion can be used to simulate the hardening and softening of geomaterials in the future numerical computation of geotechnical engineering.

In order to know the geostress characteristics of a candidate repository，in-situ stress measurement of hydraulic fracturing using a single loop system was carried out in four boreholes in granite rock. The data of geostress and the orientation of the maximum horizontal principal stress at depths ranging from 0 to 700 m below the ground surface were obtained successfully based on the information of borehole log. The geostress state and the fault activity in the candidate repository were analyzed according to the measured data，Byerlee law and Coulomb criterion for fault friction. Three principal stresses have the good linear relationships with depth. Within the range of tested depth，the horizontal stresses are generally higher than vertical stresses and the regional stress field is dominated by the tectonic horizontal stresses，which attenuate gradually with depths. The horizontal force in rock mass in the north is greater than that in the middle and south and it is the lowest in the south. The orientations of the maximum horizontal stress are dominantly in the NEE direction，which is in accordance with the direction of regional tectonic stress field. From the interior and the edge of the Tibetan plateau to the eastern Tianshan mountain，the maximum horizontal stress orientations show the variation of the NE to NEE. The geostress values do not reach the limit state of fault friction sliding and the fault activity is weak.

In order to avoid the outward waves being reflected back into the simulated domain at the artificial boundaries，the absorbing boundaries must be used in applying the granular discrete element method(PFC). To consider the various radii of particle elements on the artificial boundaries and the irregular boundary surfaces，the equivalent equation applicable for this discrete elements method was obtained based on the continuum viscous boundary condition. The calibration factors were introduced into the equivalent equation and a method to determine their values necessary for the optimum wave absorption was proposed. The joint network models of bedding and reverse bedding rock slopes were established with the synthetic rock mass approach (SRM). The viscous boundary conditions were built on the artificial boundaries in PFC models of rock slope based on the proposed method. At the same time，the seismic failure process of bedding and reverse bedding rock slopes with orthogonal secondary rock joints were simulated and systematic analyses of the seismic failure mechanism were conducted.

The fatigue tests of gypsum rock were conducted using the dynamic test system MTS 815，acoustic emission system and environmental scanning electron microscope to investigate the impact of cyclic loading on the fatigue damage characteristics of gypsum rock. The shapes of cyclic stress-strain curves of gypsum rock are different from ones of other rocks. The loading curves can be divided into a nearly linear segment with elastic characteristics and a plastic characteristics segment with depressed shapes，which show that the strains lag behind the stresses. The unloading curves exhibit largely the elastic characteristics as the curve shapes are approximately linear. The cyclic loading conditions have obvious influence on the fatigue damage properties of gypsum rock. The damage process and the macroscopic failure characteristics were revealed from the AE information and microstructure characteristics. Under the higher stress level，the larger stress upper limit and the lower loading frequency，the cyclic stress-strain curves are sparser with the larger areas of hysteretic loop in each cycle and the more AE information occur with higher AE rates. In this case，the fatigue damage rate is higher，the plastic strains are larger and the more microstructures are broken in each cycle.

The EPB shield model of Ф800 mm was used in laboratory test to study the soil disturbance induced by the shield tunneling in the upper-soft and lower-hard ground. The corresponding model of discrete element method (DEM) was established to investigate the over excavation quantitatively and other information about the disturbed ground. When tunneling is in the hard rock, the settlement surface is sector shaped，orienting towards the soft soil. When tunneling is in the soft soil, the settlement surface is funnel shaped. The surface settlement of the upper-soft and lower-hard ground is smaller than that of homogeneous soft soil，while the subsurface settlement is much larger than that of soft soil. The width parameter of subsurface settlement trough K increases exponentially along the gravitational direction，and the width parameter gets larger as the ratio of hard rock to whole tunnel face gets smaller. For the same depth，K of the upper-soft and lower-hard ground is smaller than that of the homogeneous soil. The larger proportion of hard rock the tunnel face has，the proportion of the excavated soft soil contained in the muck differs more from its theoretical value. The maximum horizontal displacement occurs at the point of inflection of vertical settlement trough.

Water inrush is a typical geologic hazard when the mountain tunnels pass through different fracture zones，and establishing the license mechanism of tunnel construction is an effective way to reduce the damage and to control risk. The license mechanism of tunnel construction is a risk control measure based on the water inflow forecast，geological prediction，plugging reinforcement measures，excavation method，construction management and comprehensive evaluation. Only when the risk of construction is within the acceptable category or the construction measures are adjusted to avoid the occurrence of disaster，the constructions will be permitted. A water inflow model was established to predict the possible water inflow when tunneling passed through the fracture zone. The scale，spatial distribution and rock characteristics of the fracture zone to be excavated in front of tunnel face were inspected accurately with the comprehensive advanced geological prediction system. The results of the geological inspection and water inflow prediction were combined with the proposed plugging reinforcement measures，excavation method，construction management and other factors together to form the evaluation index of construction license. The risk and safety of construction can be determined through the comprehensive evaluation method. This method was applied successfully to the Taining tunnel through the F2 fracture zone in construction and ensured the safety of the tunnel through the fracture zone.

The freeze-thaw action in seasonal frozen regions can lead to moisture migration in soil. When the static load is applied on the soil，the stress fields in soil change，and then the moisture contents and the pore water pressures change accordingly. The variations of pore water pressure and moisture in soil were studied with the model test under the freeze-thaw and static load actions. The test results indicate that the variation of pore water pressure is stable during the initial stage，then increases rapidly and finally varies cyclically in two cases with or without loading. The pore water pressure increases and the moisture content decreases with the depth of soil in the case without loading. Under the load condition，the pore water pressure and moisture content at the upper and the middle position of the soil body were greater than those at two sides of soil body. In a freeze-thaw cycle，the pore water pressure and moisture content increase with the temperature rising. The pore water pressure and moisture content change with temperature with a time delay.

The micropile-mechanically stabilized earth(MSE) wall suitable for roadway construction in steep terrain of mountainous areas is a new type of earth retaining structure. To validate its working mechanism and effect，model tests and numerical simulation were conducted to study the multilevel surcharge induced static response of MSE walls on slope before and after the micropile reinforcement. The results indicate that the numerical method can simulate the model tests well. Under the surcharge loadings of 2–10 kPa，the measured subsidence of micropile-MSE wall is reduced by 11%–40% compared to that of unreinforced model，whereas the wall deflection is reduced by 50%–66%. The higher the surcharge loading，the larger the reduction is. The base and lateral earth pressures are also decreased notably. The inclined micropiles in the micropile-MSE wall play a more important role in the deformation control，which lead to a 25.9%–40.3% higher bending moment in the inclined piles than in the vertical piles under the surcharge loadings of 2–10 kPa. Therefore it is necessary to use the micropiles of higher strength as the inclined reinforcement in the MSE wall. Thus，the reliability of the micropile-MSE wall is verified preliminarily .

The true triaxial tests to the undisturbed and the saturated remould soft clay from the city of Yingkou were carried out to study the effect of confining pressure and principal stress on the strength of soft clay. The stress ratio of soft clay under the three-dimensional stress conditions is presented according to the comprehensive structure potential theory and the relationship between the deviatoric stress and the generalized shear strain of the undisturbed soft clay with structural parameters is established. The curve of the deviatoric stress(q) vs the generalized shear strain( ) of undisturbed soft clay is related to the pre-consolidation pressures. It is strain softening when the confining pressures are smaller than the pre-consolidation pressures and the volumetric strain appears shear shrinkage. It is strain hardening when the confining pressures are larger than the pre-consolidation pressures and the volumetric strain appears shear dilation. The type of curves of q vs.  of the disturbed saturated soft clay is not affected by the structural yield stress and is basically the strain hardening one. The strengths of undisturbed soft clay and saturated soft clay are increased with the increasing of the confining pressure and coefficient of the principal stress. But the structural parameters of stress ratio decreased with the increasing of the shear strain，confining pressure and coefficient of the principal stress. The structural parameters of stress ratio varies logarithmically with the generalized shear strain. The structural parameters of stress ratio was introduced into the q-  curves of undisturbed soft clay and the curves were thus obtained. The relationship between the deviatoric stress and the generalized shear strain for undisturbed soft clay was established and it has a good agreement with the experimental results.

The research of pile foundation in loess subsoil is insufficient. The first super high-rise building in Longdong was investigated with the concrete strain meters and stress gauges installed on the pile body，and the soil pressure cells placed under the pile cap and pile tip. The software ANSYS was used to analyze the raft settlement of the whole short pile，the whole long pile and the composite pile foundation with long and short piles and to analyze the stress field and settlement variation of soil foundation. The ground soil has the collapsible and non-collapsible loess layers. The non-collapsible loess may become collapsible. The soil layers around the pile has the major effect on the transmission and distribution of the internal pile force. There are several neutral points on the pile body，so the determination of the lower limit of collapsible soil is more complicated. Under the different load levels，the Q-S curves of the piles vary slowly, indicating that the piles are frictional ones. The internal force of pile body develops asynchronously. When the test load reaches up to 8 000 kN，the maximum settlement on the pile top is 8.15 mm and the resistance of the single pile and single pile cap is 4.8% and 2.1% of load on pile top respectively. The measured reaction force at cushion cap of the single pile shapes like an inverted basin and the edge stress is relatively greater. The load carrying properties of pile-soil-cushion cap system are better than the one of single pile foundation. The composite pile foundation with long and short piles makes the full use of the settlement control ability of long pile and the shallow bearing ability of foundation soil to reduce the number of long piles which reduces the cost of pile foundation.

To avoid the disturbing to the existing underground structures，shield advancing along a path with a small radius of curvature is sometimes inevitable. In this paper，the site observation data，the vertical and horizontal deformation and the pore water pressure of soils around the tunnel，were presented and analyzed when a shield advancing through a path with the radius of curvature being 118 m. It was found that the soil deformation mode was very different from those observed in the case of straight path. The soil around the tunnel on the outside of the curve was squeezed and moved upward and the horizontal displacement of soil around the tunnel consists of two parts. One part was induced by the squeezing effect，which was similar to that induced by shield advancing through a straight path，and the other part was from the turning action. The second part is nonsymmetrical. The soil on the outside of the curve moved away from the tunnel and the soil on the inside moved towards the center of the tunnel. The superimposition of the deformation increased the risk and should be paid more attention.

In order to evaluate the characteristics of stiffness decay of expansive soil at the in-situ stress state under the small strain condition，the in-situ seismic dilatometer test and the resonant column test are carried out to analyze the influence of stress history，stress state and disturbance on the modulus decay of expansive soil. Results show that both the stress state and stress history significantly affect the shear modulus of expansive soil. The shear modulus increases with the increasing of the confining pressure under the same stress path and the modulus decays faster with the development of shear strain. The shear modulus of soils following the loading-unloading path is greater than that of soils only following the loading path，while the G-? decay curve of former is nearly the same as that of soils following the loading-unloading-reloading path. Besides，the in-situ shear modulus is greater than that from the resonant column tests of the same stress history，which indicates that disturbance caused by sampling，unloading，transportation and sample preparation contributes to the irreversible damage，so that the in-situ characteristics were not be presented in the indoor test results following the loading and unloading path. The in-situ G-? decay curves derived with different reference strains exhibit an evident difference in the middle strain range，which shows the shear modulus decays faster with smaller reference strain. Selecting a reasonable reference curve and the shear modulus of small strain are the key to get the right in-situ G- decay curves.